The present invention relates to a cable detector which searches a communication cable and/or a power cable installed under water, in particular, it relates to structure of a cable sensor mounted on a cable detector.
When there is something wrong with a cable under water, the damaged portion of the cable is lifted on to a boat and repaired.
The conventional cable detector is anchor type as shown in the Japanese patent laid open publication No. 26017/80.
FIGS. 5 and 6 show that conventional cable detector. In FIG. 5, the cable detector has a cylindrical main body 60 which has radially extended legs 61 at one end of the main body. The main body 60 has a rope connector 62 at which a rope for pulling the cable detector is fixed. The main body 60 has hollow room, where a water tight switch 63 which indicates the presence of a cable is mounted. At one end of each leg 61, is provided a bearing 64 which supports a movable slide rod 65. Each slide rod 65 has a cable sensor 66 on one end, and the other end of the rod 65 is fixed to the common support 67, which has a slidable rod 69 at the center of the same. The nut 68 fixes the rod 69 to the common support 67. The rod 69 has a spring stopper 70 at the other end. A coil spring 71 is provided around the rod 69. One end of the coil spring 71 is fixed to the stopper 70, and the other end of the spring 71 touches with the end of the main body 60.
When the cable detector of FIGS. 5 and 6 is pulled by a boat so that the cable detector runs perpendicular to the cable to be detected, one of the legs 61 is engaged with the cable 72. Then, the cable sensor 66 at one end of the leg is pushed by the cable, and shifts in the opposite direction of the moving direction of the cable detector. Therefore, the slide rod 65 slides, and the common support 67 and the slide rod 69 shift. The shift of the rod 69 pushes the coil spring 71, and actuates the switch 63, which transmits the sense signal to the boat through a signal transmission cable (not shown). Thus, the boat can detect the presence of a cable through the electrical signal by the switch 63.
However, the conventional cable detector described above has the disadvantages as follows.
When the radially extended legs 61 engage rocks on the sea bed, the cable detector operates incorrectly, and indicates as if there was a cable. Further, when the shape of the sea bed is irregular, the legs can not follow the profile of the sea bed, and miss cables.
Therefore, the conventional cable detector is not reliable, and takes long time to search for a cable.